linux-kernel - Re: [PATCH v2 1/1] firmware_loader: Fix use-after-free during unregister

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Date:   Mon, 29 Aug 2022 14:49:11 -0700 (PDT)
From:   matthew.gerlach@...ux.intel.com
To:     Russ Weight <russell.h.weight@...el.com>
cc:     mcgrof@...nel.org, gregkh@...uxfoundation.org, rafael@...nel.org,
        linux-kernel@...r.kernel.org, trix@...hat.com, lgoncalv@...hat.com,
        basheer.ahmed.muddebihal@...el.com, tianfei.zhang@...el.com,
        kernel test robot <oliver.sang@...el.com>
Subject: Re: [PATCH v2 1/1] firmware_loader: Fix use-after-free during
 unregister



On Mon, 29 Aug 2022, Russ Weight wrote:

> In the following code within firmware_upload_unregister(), the call to
> device_unregister() could result in the dev_release function freeing the
> fw_upload_priv structure before it is dereferenced for the call to
> module_put(). This bug was found by the kernel test robot using
> CONFIG_KASAN while running the firmware selftests.
>
>  device_unregister(&fw_sysfs->dev);
>  module_put(fw_upload_priv->module);
>
> The problem is fixed by copying fw_upload_priv->module to a local variable
> for use when calling device_unregister().
>
> Reported-by: kernel test robot <oliver.sang@...el.com>
> Fixes: 97730bbb242c ("firmware_loader: Add firmware-upload support")
> Signed-off-by: Russ Weight <russell.h.weight@...el.com>

Looks good to me.

Reviewed-by: Matthew Gerlach <matthew.gerlach@...ux.intel.com>
> ---
> v2: Rebased to latest linux-next branch (next-20220829)
> ---
> drivers/base/firmware_loader/sysfs_upload.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/base/firmware_loader/sysfs_upload.c b/drivers/base/firmware_loader/sysfs_upload.c
> index 87044d52322a..63e15bddd80c 100644
> --- a/drivers/base/firmware_loader/sysfs_upload.c
> +++ b/drivers/base/firmware_loader/sysfs_upload.c
> @@ -377,6 +377,7 @@ void firmware_upload_unregister(struct fw_upload *fw_upload)
> {
> 	struct fw_sysfs *fw_sysfs = fw_upload->priv;
> 	struct fw_upload_priv *fw_upload_priv = fw_sysfs->fw_upload_priv;
> +	struct module *module = fw_upload_priv->module;
>
> 	mutex_lock(&fw_upload_priv->lock);
> 	if (fw_upload_priv->progress == FW_UPLOAD_PROG_IDLE) {
> @@ -392,6 +393,6 @@ void firmware_upload_unregister(struct fw_upload *fw_upload)
>
> unregister:
> 	device_unregister(&fw_sysfs->dev);
> -	module_put(fw_upload_priv->module);
> +	module_put(module);
> }
> EXPORT_SYMBOL_GPL(firmware_upload_unregister);
> -- 
> 2.25.1
>
>